An imaging device including a pixel unit which performs photoelectric conversion and which has pixels arranged thereon in a matrix each configured to output a signal based on incident light, and a column-parallel analog-digital conversion unit in which an analog-digital conversion unit is located so as to correspond to each column of pixels (hereinafter, an analog-digital conversion unit is referred to as an ADC (Analog Digital Converter), and a column-parallel ADC is referred to as a column ADC) is conventionally known. In the column ADC, a circuit unit for each column performs analog-digital conversion (hereinafter referred to as AD conversion) to convert analog signals output from the pixels (an analog signal output from a pixel is hereinafter referred to as a pixel signal) into digital signals.
PTL 1 describes an imaging device including a pixel having a plurality of photoelectric conversion units that convert optical signals into signal charge and accumulate the signal charge and one amplification MOS transistor that, upon receiving signal charge from each of the plurality of photoelectric conversion units, outputs a signal corresponding to the signal charge. A pixel 1 described in PTL 1 outputs to a vertical signal line a first signal with a noise level (hereinafter referred to as an N signal) which is output from the pixel, a second signal (hereinafter referred to as an A+N signal) based on first signal charge to be accumulated in at least one photoelectric conversion unit, and a third signal (hereinafter referred to as an A+B+N signal) based on signal charge obtained by further adding signal charge to be accumulated in another photoelectric conversion unit to the first signal charge. The A+N signal is held in each of a first capacitor and a second capacitor which are electrically connected to the vertical signal line. The A+B+N signal is held in a third capacitor which is electrically connected to the vertical signal line 8.